The structures of a group of triorganotin sulphates and chromates have been studied by 119Sn n.m.r. and Mössbauer spectroscopies. All the compounds (SnR3)2EO4·nH2O (R = Me, E = Cr, n= 0; R = Me or Bun, E = S, n= 0; R = Me, E = S, n= 2) form polymeric lattices in the solid state, although for (SnBun3)2SO4 an irregular lattice incorporating both four- and five-co-ordinate tin atoms is postulated. The structure of (SnMe3)2SO4·2H2O has been determined by an X-ray study. Crystal data: orthorhombic, space group Pbcn, a= 11.245(4), b= 12.695(5), c= 10.811(4)Å, Z= 4. The geometry about tin is trigonal bipyramidal with a trans-O2SnC3 stereochemistry about the metal, one of the axial sites being occupied by a molecule of hydration. Hydrogen bonding between oxygens of the anion and the solvate produces a three-dimensional network lattice.